yogabook / bones / os peroneum

The Os peroneum (also: Os peroneale, Sesamum peronaeum) is a sesamoid bone occurring in around a quarter of people in the distal half of the insertion tendon of the fibularis longus on the lateral plantar side of the Os cuboideum. The incidence varies greatly (5-30%, with 60% bilateral and 30% biparita or tripartita), but it is probably the most common accessory bone of the tarsus alongside the trigonum and external tibial bone.

Painful conditions associated with the os peroneum are referred to as painful os peroneum syndrome (POPS). They can be caused by a fracture of the os peroneum, by indirect (secondary) fracture healing of a fracture or by tendosynovitis of the fibularis longus attachment tendon caused by the bone. It can also be caused by an oversized tuberculum peronei of the calcaneus, which pinches the os peroneum or the fibularis longus attachment tendon. Mechanical irritation caused by extensive running training, for example, is also possible.